The present invention relates to a precise positioning actuator for a head element such as a thin-film magnetic head element or an optical head element, to a head gimbal assembly (HGA) with the actuator and to a manufacturing method of an HGA.
In a magnetic disk drive apparatus, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of HGAs, respectively.
Recently, recording and reproducing density along the radial direction or along the track width direction in the magnetic disk (track density) rapidly increase to satisfy the requirement for ever increasing data storage capacities and densities in today""s magnetic disk drive apparatus. For advancing the track density, the position control of the magnetic head element with respect to the track in the magnetic disk by a voice coil motor (VCM) only has never presented enough accuracy.
In order to solve this problem, an additional actuator mechanism is mounted at a position nearer to the magnetic head slider than the VCM so as to perform fine precise positioning that cannot be realized by the VCM only. The techniques for realizing precise positioning of the magnetic head are described in for example U.S. Pat. No. 5,745,319 and Japanese patent publication No. 08180623 A.
As for a precise positioning actuator, there are various structures of actuator such as for example a load-beam structure actuator and a piggyback structure actuator.
The load-beam structure actuator has two piezoelectric elements of PZT attached on a load beam of a suspension. These PZT elements are driven in a manner to support with each other to displace the load beam so as to perform fine precise positioning of magnetic head slider mounted on the load beam.
The piggyback structure actuator is formed by piezoelectric material of PZT in an I-character shape with one end section to be fixed to a suspension, the other end section to be fixed to a magnetic head slider and a pillar shaped movable arm connected between these end sections. The PZT is driven to perform fine precise positioning of the magnetic head slider directly attached to this actuator. On the suspension, stepwise stacked are the actuator and the magnetic head slider, namely, the actuator is caught between the suspension and the slider to form a stacked cantilever structure.
However, the aforementioned conventional precise positioning actuators had following various problems:
(1) Mechanical resonance was occurred at a relatively low frequency;
(2) Since the actuator as a whole consists of piezoelectric material such as PZT of a brittle material, shock resistance is very poor. Particularly, since in case of a piggy-back structure actuator, the actuator and the magnetic head slider are stacked to form a cantilever structure, a shock easily occurs with a moment and also shock resistance is extremely poor;
(3) Depending upon the size of the magnetic head slider, a travel of the magnetic head element during the precise positioning operation varies. Thus, it is difficult to obtain enough stroke;
(4) Handling at the time of an assembly of the HGA is very difficult;
(5) Particularly, in case of a piggy-back structure actuator, because of the stepwise stacked structure, a total thickness of the HGA around the magnetic head slider increases by the thickness of the actuator;
(6) In case of a piggy-back structure actuator, because of three-dimensional and complicated attachment structure, the handling at the time of an assembly of the HGA is extremely difficult and it is impossible to use a conventional HGA assembly equipment causing productivity to be very worse; and
(7) In order not to interfere with the movement of the piggy-back structure actuator, it is necessary to assemble with keeping a gap between the actuator and the magnetic head slider and also between the actuator and the suspension. However, forming of such gaps will more decrease the shock resistance and it is difficult to precisely keep the gaps constant. Particularly, since it is difficult to keep the suspension, the actuator and the magnetic head slider in parallel precisely, the head characteristics deteriorates.
To solve the aforementioned various problems, the inventors of this application had proposed an actuator provided with a pair of metal plate movable arms for fixing and catching a magnetic head slider in a space between the movable arms (U.S. patent Ser. No. 09/972,939 now pending).
However, this actuator has the structure for catching side surfaces of the magnetic head slider in the movable arms and thus has the following problems:
(A) It is difficult to fix the magnetic head slider with a sufficient strength;
(B) A resistance against a shock toward its up-and-down directions that intersect the magnetic disk surface is extremely poor; and
(c) It is impossible to commonly adopt magnetic head sliders with different width, namely different distances between the side faces, from that of the standard magnetic head slider.
It is therefore an object of the present invention to provide a precise positioning actuator for a head element, an HGA with the actuator and a manufacturing method of an HGA, whereby fixing between the actuator and a head slider can be achieved with a sufficient strength.
Another object of the present invention is to provide a precise positioning actuator for a head element, an HGA with the actuator and a manufacturing method of an HGA, whereby a shock resistance toward up-and-down directions can be greatly improved.
Further object of the present invention is to provide a precise positioning actuator for a head element, an HGA with the actuator and a manufacturing method of an HGA, hereby a head slider with a different size from a standard head slider can be easily mounted to the actuator.
According to the present invention, a precise positioning actuator to be fixed to a head slider provided with at least one head element and to a support, for precisely positioning the at least one head element includes a pair of movable arms and a coupling section. Each movable arm is formed by a metal plate to be substantially in parallel with a side surface of the head slider. Top end sections of the pair of movable arms are capable of displacing in response to a drive signal applied to the actuator along a direction crossing planes of the metal plate. The coupling section is connected between the top end sections of the pair of movable arms and formed by a metal plate to be substantially in parallel with a first surface of the head slider. This first surface is opposite to an air bearing surface (ABS) of the head slider. The first surface of the head slider is to be fixed to the coupling section.
Since the actuator is provided with a coupling section connected between the top end sections of the pair of movable aims and the head slider is to be fixed to this coupling section, fixing of the slider can be achieved with sufficient strength and a shock resistance against up-and-down movements can be greatly improved. Also, head sliders with different widths can be easily mounted to the actuator.
Further, the movable arms and the coupling section are mainly made from a metal plate, the weight of the whole actuator can be reduced and thus a mechanical resonance frequency of the actuator can be increased. Also, as a basic member of the arms is formed by the metal plate that is strong and light-weighted, a shock resistance of the movable arms that are particularly weaken for the shock can be greatly improved. Due to the usage of the metal plate provided with a high mechanical strength, treatment of the actuator during assembling of the HGA becomes very easy. By using the metal plate to form the main portion of the actuator, the flexibility on a design of the actuator will improve with the shape and/or size. Thus, it is enabled to design the actuator with a sufficient stroke. Furthermore, because the metal plate can be precisely machined, accuracy in size of the actuator itself can be greatly improved.
Also, since the head slider will be mounted in a space between the movable arms, the thickness of the HGAL around the head slider does not increase even if the actuator is attached. Thus, no modifications in size of the disk drive apparatus due to the mounting of the actuator is necessary.
In addition, since the head slider is caught in between the movable arms, the top end sections of the movable arms, which actually transfer the displacement to the slider, can be extended to always position at the top end of the slider. Thus, it is possible to provide a constant travel to the slider even if the size of the head slider changes, and therefore an enough stroke of the head at the precise positioning operation can be always obtained.
Because of a partial fixing of the head slider to the coupling section of the actuator, shape change in the ABS of the head slider (generation of crown or camber) can be prevented from occurring even if the adhesive deforms due to change in atmosphere temperature.
It is preferred that the actuator further includes a base section formed by a metal plate that is in parallel with the coupling section, and fixed to the support, the pair of movable arms extending forward from the base section. As not only the movable arms and the coupling section but also the base section are made from a metal plate, the weight can be more reduced and a shock resistance can be more improved. Also, accuracy in size of the actuator itself can be greatly improved.
It is also preferred that the pair of movable arms also extend backward from the base section.
It is preferred that the pair of movable arms, the base section and the coupling section have a U-shaped section structure formed by bending a single metal plate. Since the main portion of the actuator is configured by bending a single metal plate, its fabrication becomes easy and a mechanically strong actuator can be provided.
It is further preferred that the base section has a strip shape or that the base section includes a strip and a projection protruded forward form the strip.
It is also preferred that the coupling section has a strip shape or that the coupling section includes a strip and a projection protruded forward from the strip. Preferably, the coupling section further includes lateral jutting portions protruded from the projection so as to operate as a limiter for preventing a top end section of the actuator from excessively moving toward up-and-down directions when a shock is applied.
It is preferred that each of the pair of movable arms consists of an arm member made of the metal plate, and a piezoelectric element formed or adhered on a side surface of the arm member. In this case, the piezoelectric element has a multi-layered structure or a single layer structure of a piezoelectric material layer and of an electrode layer. If the piezoelectric element is formed in the multi-layered structure, sufficient displacement will be obtained at low drive voltage and a horizontal shock resistance will be increased.
It is preferred that the metal plate is a stainless steel plate.
It is more preferred that conductor traces for transmitting signals of the head element are formed on the pair of movable arms. Since the trace conductors connected to head element connection pads are formed on the movable arms, all the trace conductors connected to the head element and the actuator can be provided by a conductor pattern fabricated in the same process. Therefore, the traces become simple and also the manufacturing cost can be reduced. Furthermore, since the signal conductor traces are adhered in parallel on the movable arms, the movement direction of the arms intersect the plane of the conductor traces. Thus, not only the resistance against the displacement of the movable arms will decrease but also the trace conductors will not forcedly bend causing no damage to them.
It is preferred that the at least one head element is at least one thin-film magnetic head element.
According to the present invention also an HGA includes a head slider provided with at least one head element, a support and above-mentioned precise positioning actuator fixed to the head slider and to the support.
It is preferred that the coupling section of the actuator and the head slider are fixed by adhering. More preferably, the coupling section of the actuator and the head slider are adhered by a conductive adhesive. In case of using a conductive adhesive, the body of the head slider can be easily grounded through the actuator. It is also preferred that the actuator and the support are fixed by adhering or by laser welding.
According to the present invention further, a manufacturing method of an HGA includes a step of preparing a head slider provided with at least one head element, a support and a precise positioning actuator having a pair of movable arms each formed by a metal plate to be substantially in parallel with a side surface of the head slider, top end sections of the pair of movable arms being capable of displacing in response to a drive signal applied to the actuator along a direction crossing planes of the metal plate, a coupling section connected between the top end sections of the pair of movable arms and formed by a metal plate to be substantially in parallel with a first surface of the head slider, the first surface being opposite to an ABS of the head slider, and a base section formed by a metal plate that is in parallel with the coupling section, the pair of movable arms extending forward from the base section, a step of fixing the first surface of the head slider to the coupling section of the actuator, and a step of then fixing the base section of the actuator with the head slider to the support.
First, the head slider is fixed to the coupling section of the actuator, and then the actuator with the head slider is fixed to the support. Since assembling of the head slider and the actuator can be carried out on the flat plate, alignment of the slider and the actuator becomes easy resulting that a higher accuracy assembling can be expected. Also, since a thermosetting adhesive with excellent curing performance although it needs a long curing time can be used, a high quality assembly of the head slider and the actuator can be obtained. Furthermore, since the assembly has a simple shape, adhesion and electrical connection of the assembly with a suspension can be performed by using a general HGA assembling equipment resulting the productivity to extremely improve and thus the manufacturing cost to reduce. In addition, due to the usage of the metal plate provided with a high mechanical strength, treatment of the actuator during assembling of the HGA becomes very easy. Further, as aforementioned, fixing of the slider can be achieved with sufficient strength and a shock resistance against up-and-down movements can be greatly improved. Also, head sliders with different widths can be easily mounted to the actuator.
Also, according to the present invention, a manufacturing method of an HGA includes a step of preparing a head slider provided with at least one head element, a support and a precise positioning actuator having a pair of movable arms each formed by a metal plate to be substantially in parallel with a side surface of the head slider, top end sections of the pair of movable arms being capable of displacing in response to a drive signal applied to the actuator along a direction crossing planes of the metal plate, a coupling section connected between the top end sections of the pair of movable arms and formed by a metal plate to be substantially in parallel with a first surface of the head slider, the first surface being opposite to an ABS of the head slider, and a base section formed by a metal plate that is in parallel with the coupling section, the pair of movable arms extending forward from the base section, a step of fixing the base section of the actuator to the support, and a step of then fixing the first surface of the head slider to the coupling section of the actuator.
Since the base section and the movable arms extending forward from the base section of the actuator are formed by a metal plate, the mechanical strength of the actuator become high. Thus, treatment of the actuator during assembling of the HGA becomes very easy. Further, as aforementioned, fixing of the slider can be achieved with sufficient strength and a shock resistance against up-and-down movements can be greatly improved. Also, head sliders with different widths can be easily mounted to the actuator.
It is preferred that the method further includes a step of inserting a spacer between the base section of the actuator and the head slider before the step of fixing the head slider to the coupling section. By using the spacer, necessary gap can be very easily formed.
It is also preferred that the step of preparing the actuator includes bending a metal plate to form the pair of movable arms, the coupling section and the base section. Since the main portion of the actuator is configured by bending a single metal plate, its fabrication becomes easy and a mechanically strong actuator can be provided.
Further objects and advantages of the present invention will be apparent form the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.